Biochemical oxygen demand (BOD) represents the amount of oxygen consumed by bacteria and other microorganisms while they decompose organic matter under aerobic (oxygen is present) conditions at a specified temperature.
What is biochemical oxygen demand and why is it important?
The BOD is an important parameter for assessing water quality. It deals with the amount of oxygen consumption (mg O2 L− 1) by aerobic biological organisms to oxidize organic compounds. Sewage with high BOD can cause a decrease in oxygen of receiving waters, which in turn can cause the death of some organism.
What is good Biological Oxygen Demand?
A BOD level of 1-2 ppm is considered very good. There will not be much organic waste present in the water supply. A water supply with a BOD level of 3-5 ppm is considered moderately clean.
What is biochemical oxygen demand class 11?
Biochemical oxygen demand: It is the amount of oxygen required by bacteria to carry out the decomposition of the organic matter present in a certain volume of a sample of water. It gives us an idea of the amount of organic matter present in water. Lesser the BOD in water, the more clean it would be.
What is BOD and How Is It measured?
The BOD test is a bioassay technique involving the measurement of oxygen consumed by the bacteria while stabilizing the organic matter in the waste as they would normally do in nature but under normal laboratory conditions. By convention, the test is conducted for a period of 5 days at 20°C (68°F).
What causes high BOD in wastewater?
Sources: BOD represents the amount of organic matter in a water supply; therefore, it increases when decaying plants, human or animal waste, and other organic compounds are added to water.
What happens when BOD is high?
The greater the BOD, the more rapidly oxygen is depleted in the stream. This means less oxygen is available to higher forms of aquatic life. The consequences of high BOD are the same as those for low dissolved oxygen: aquatic organisms become stressed, suffocate, and die.
Why is COD so important?
In wastewater treatment, the Chemical Oxygen Demand (COD) is an important measurement for the amount of oxygen that is required to break down pollutants (organic substances) in water. The chemical oxygen demand can be measured using different methods, direct or indirect.
What is the BOD value of pure water?
UPLOAD PHOTO AND GET THE ANSWER NOW! Solution : A pure water would have about 1 ppm value. A water supply with BOD level of 3.5 ppm is moderately clean, and water with a BOD level of 6.9 ppm is considered as polluted water.
How is BOD removed from wastewater?
You can reduce COD and BOD by adding hydrogen peroxide to the wastewater solution. The hydrogen peroxide will chemically attack the organics in the wastewater, degrading them and reducing the measured COD and BOD.
What is biochemical oxygen demand BOD test?
The test for biochemical oxygen demand (BOD) is a bioassay procedure that measures the oxygen consumed by bacteria from the decomposition of organic matter (Sawyer and McCarty, 1978). The change in DO concentration is measured over a given period of time in water samples at a specified temperature.
What is Biological Oxygen Demand PDF?
waste matter in wastewater is known as biological oxygen demand or biochemical oxygen demand. Therefore it is used to measure the amount of certain type of organic water pollution BOD is. calculated by keeping a sample of water containing a known amount of oxygen for five days at 20. °C.
What increases the BOD of water?
Organic loading is occurrence of excess organic matter inside water due to sewage disposal and eutrophication. This leads to an increase in biological oxygen demand (BOD) for putrefaction. Explosive multiplication of alga leads to algal bloom.
How do you calculate BOD of water?
For example: 1.0 mL of a full strength wastewater sample added to 9.0 mL of DI water results in a 0.1 dilution of the wastewater. The DO concentration (mg/L) reduction must then be multiplied by 10 to determine the final BOD concentration.
Does BOD increase with temperature?
The BOD removal rate in the bioreactor increased when the temperature increased from 20 degrees C to 30 degrees C, 40 degrees C, and 50 degrees C, but it decreased when the temperature increased from 50 degrees C to 60 degrees C. Higher temperature enhanced the endogenous respiration of microbes in the bioreactor.
What does low BOD mean?
Inversely, low BOD means less oxygen is being removed from water, so water is generally purer. Cold water retains oxygen better than warmer water, so in summer months, dissolved oxygen is usually lower from the start.
Does high BOD mean pollution?
BOD indicates the amount of organic matter present in water. Therefore, a low BOD is an indicator of good quality water, while a high BOD indicates polluted water.
What is COD load?
Chemical Oxygen Demand (COD) was defined as the measured amount of oxygen needed to chemically oxidise the organics present in wastewater. The less polluted the wastewater is, the less oxygen needed to chemically oxidise the organics present hence the less or smaller the COD value.
What food is COD?
Cod is a fish with flaky, white flesh and a mild flavor. It’s packed with protein, B vitamins, and minerals. However — unlike many other types of seafood — cod is not often promoted as a health food, so you may wonder whether it’s good for you.
What is a COD fee?
The Collect on Delivery (COD) fee is determined by the amount to be collected OR amount of insurance coverage desired (whichever is higher). The Collect on Delivery fee is not eligible for a refund.
What is BOD value per Litre in sewage water?
The amount of oxygen required by bacteria to break down the organic matter present in a certain volume of a sample of water, is called Biochemical Oxygen Demand (BOD). It is measured in ppm. The BOD of municipal sewage is 100-4000 ppm.
Does chlorine reduce BOD?
BOD reduction: Chlorine accomplishes BOD reduction by oxidation of organic compounds present in wastewaters. 4. Oxidation of metal ions: Metal ions which are in reduced state are oxidized by chlorine (e.g., ferrous to ferric ion and manganous to manganic ions).
Does aeration reduce BOD?
Aeration is used to operate activated sludge process units and is perhaps the most frequently used process to remove biochemical oxygen demand (BOD) from wastewater.
Why is BOD test done for 5 days?
BOD occurs in 2 general stages. While calculating the oxygen demand, the carbonaceous stage is taken into account. This stage is almost completed in 5 days, which means that most of the organic content of the sewage is oxidized under aerobic conditions in 5 days. Hence ,BOD for 5 days is calculated.
What are the limitations of BOD test?
Limitations Of Test The method takes five days to perform and uses a discrete sample. The test has poor reproducibility and toxic chemicals can inhibit measurement. Short-term BOD determinations magnify errors and still require relatively long sample periods. The test is not suited for on-line, continuous measurement.